NEGATIVE-ELECTRODE ACTIVE MATERIAL FOR SECONDARY BATTERIES, AND SECONDARY BATTERY

A negative electrode active material for a secondary battery includes an intermetallic compound having a cage structure. The cage structure is constituted of at least one first atom located within a cage, and a plurality of second atoms arranged in a cage-like form so as to surround the first atom. The first atom is a cerium atom, and the plurality of the second atoms include 8 or more and 17 or less silicon atoms.